1. The formation of a regular polymer with regular double bonds contributes to the usefulness of the ROMP process. State true or false.
a) true
b) false
Explanation: The ROMP process is useful because of the formation of a regular polymer with regular number of double bonds. Thus the final product is available for the partial or total hydrogenation to form more complex compounds.
2. Which of the following mechanism can produce a copolymer?
a) step-growth mechanism
b) free radical mechanism
c) cationic mechanism
d) all of the mentioned
Explanation: Copolymers can be produced by both step-growth mechanism and chain- growth mechanism, which can occur by free radical as well as ionic mechanisms.
3. How is the reactivity of a chain radical practically determined in a free radical copolymerization?
a) number of the monomers present
b) free radical bearing terminal monomer unit
c) size of the monomer unit
d) chemical nature of monomer unit
Explanation: The reactivity of a chain radical in free radical polymerization is practically determined by the free radical bearing terminal monomer unit. The size and chemical nature of the part preceding the radical bearing terminal unit is of very little significance.
4. How many propagation reactions occur simultaneously in a binary copolymerization process?
a) 2
b) 4
c) 1
d) 3
Explanation: In binary copolymerization, there are two different chain radicals which can add both the monomers, though not necessarily with same ease, the system characterizes four simultaneous propagation reactions.
5. What does the copolymer composition depend upon, in binary copolymerization?
a) feed monomer composition
b) initiator concentration
c) rate of polymerization
d) all of the mentioned
Explanation: It is clear from the copolymer equation that copolymer composition is dependent on the feed monomer composition.
{[M1]/[M2]}copolymer = {[M1/[M2]}(r1[M1]+[M2])/(r2[M2]+[M1])
Also, there is absence of initiator and termination rate constants in the copolymer equation, which makes the composition independent of these terms.
6. Consider the copolymer equation of binary copolymerization between monomers M1 and M2
{[M1]/[M2]}copolymer = {[M1/[M2]}(r1[M1]+[M2])/(r2[M2]+[M1])
What does the term [M1] on the right hand signify here?
a) absolute molar concentration of monomer M1
b) molar concentration of monomer M1 in feed
c) molar concentration of monomer M1 in copolymer
d) none of the mentioned
Explanation: The term [M1] on the right hand side is the molar concentration of monomer M1 in the feed or reaction mixture.
7. In most cases, the copolymer composition is not measurably affected due to the presence of solvents and additives. State true or false.
a) true
b) false
Explanation: The composition is controlled by the kinetic factors, i.e. the reactivity ratios, r1 and r2, which are not affected by the initiator concentration, rate of polymerization and presence of solvents or additives. So the copolymer composition remains unaffected by such factors.
8. Which of the following has more priority, in binary copolymerization involving monomers M1 and M2, if the reactivity ratio r1 is greater than 1?
a) chain radical ∙M1 to add monomer M1
b) chain radical ∙M1 to add monomer M2
c) chain radical ∙M2 to add monomer M1
d) chain radical ∙M2 to add monomer M2
Explanation: The reactivity ratio r1 is given by-
r1= k1,1/k1,2
i.e. the ratio of homo-propagation rate constant to cross propagation rate constant, involving the chain radical ∙M1. When r1 is greater than 1, it signifies that chain radical ∙M1 has a preference to add monomer M1.
9. The values of reactivity ratios, r1 and r2 are independent of the change in the mechanism of chain propagation, form radical to ionic mechanism. State true or false.
a) true
b) false
Explanation: The values of reactivity ratios significantly change for a drastic change in the mechanism of chain propagation from free radical to ionic, and even from cationic to anionic mode of chain propagation
10. How is the monomer units arranged generally, in the copolymer structure of any vinyl copolymer?
a) sequentially
b) alternatively
c) randomly
d) all of the mentioned
Explanation: In general, the monomer units in a copolymer structure are arranged in a random manner.